Wet spinning apparatus including filament wiping means



NOV. 10, 1959 J, BROWN ETAL 2,911,674

WET SPINNING APPARATUS INCLUDING FILAMENT WIPING MEANS Filed Aug. 20, 1954 K 7 617014411 7 J00 WA/M/G wry/To s United States Patent WET SPINNING APPARATUS INCLUDING FILAMENT WIPING MEANS Application August 20, 1954, Serial No. 451,190

Claims priority, application Great Britain September 2, 1953 5 Claims. (Cl. 18-8) This invention relates to textile processes, and especially to the manufacture of artificial filamentary materials by wet-spinning processes.

In U.S. application Serial No. 323,788, filed December 3, 1952, of P. F. C. Sowter and F. B. Hill, and U.S. application 'Serial No. 451,191, filed August 20, 1954, of R. I. Brown and J. Downing, the present applicants, there are described wet-spinning processes in which the filaments formed travel under specified conditions in the same direction as the coagulating liquid up a narrow tube, and are drawn from the tube as a bundle such as a yarn or tow (hereinafter referred to as a yarn). The bulk of the coagulating liquid overflows at the top of the tube and may be collected and drawn off in any suitable way, but a substantial proportion is carried up to a considerable height by the travelling yarn unless some means for preventing this is adopted. This phenomenon is indeed observed in any textile process in which a yarn is drawn fairly fast upwardly out of a narrow tube containing a liquid. The tension imparted to the yarn by the weight of the liquid carried up may have an adverse effect on its textile properties.

One way of removing a considerable part of the liquid from the yarn, and so preventing the yarn from carrying up a large weight of the liquid, is to fix a yarn guide or the like directly above the open end of the tube to wipe the liquid off the yarn, but we have found that this also can be undesirable in that it tends to increase the number of broken filaments in the yarn. 4

U.S. application Serial No. 217,816, filed March 27, 1951, of S. G. Hawtin and J. W. Grebby, describes'a device comprising a pulley set skew with respect to the plane of the yarn over which the yarn passes after leaving the tube; this pulley has the effect of inserting a false twist in the yarn, by virtue of which the amount of liquid carried up is very much reduced. However, the insertion of this false twist is not always desirable, nor is the presence of the skew pulley always convenient.

The reason why the use of a yarn guide tends to cause filament breakage appears to be obvious, namely the friction exerted by the guide on the as yet weak and tender filaments. We have however now found that in fact this is not the main cause, and that the friction in itself has little or no deleterious effect. The main cause is, we have discovered, that the liquid which has been wiped off from the filamentary material in falling back to the tube causes disturbances in the surface of the liquid Welling up out of the tube which, though they may be quite small, are sufficient seriously to weaken or actually to break a proportion of the filaments leaving the tube.

The present invention therefore consists in textile processes, especially wet spinning processes, which comprise drawing filamentary material up and out of a substantially vertical narrow tube through which a liquid is flowing, wiping adherent liquid from the material shortly after it has left the tube, and directing at least the greater part of the liquid wiped off the material clear of the upper end of the tube.

2,911,674 Patented Nov. 10, 1959 The means whereby the liquid is directed clear of the tube is preferably an inverted conical funnel above or partlyabo've and coaxial with the tube, the diameter of the basejof the funnel being greater than that of the upper 'end of the tube. While it is better that the funnel should have a stem, this is preferably short, usually less than 1 inch long. If desired the diameter of the stem and apex of the funnel may be only slightly greater than thatof the yarn or other filamentary material being spun, so that the apex and stem. of the funnel serve to wipe'adherent liquid off the material while the conical part directs the liquid clear of the tube. We prefer however that the diameter of the stem should be suflicient to allow the filamentary material to pass through with a substantial clearance, e.-g. a clearance of about ,5 to inch all round, and to provide separate means, such as a pigtail guide above the funnel, as at least the main means whereby liquid is wiped off the material. For most purposes a diameter below 0.25 inches is satisfactory.

The basal diameter of the funnel is preferably at least twice as great as the diameter of the upper end of the tube, for example between about three and ten times as great. For instance, if the diameter at the top of the tube is 0.3-0.5 inch, the basal diameter of the funnel may be about 1.5-2.5 inches. The angle of the wall of the funnel to the vertical may be between about 20 and and is preferably between about 25 and 45" or 50". The optimum height of the apex of the funnel above the end of the tube varies a little with the rate of travel of the filaments and the linear speed of the liquid flowing up the tube, but is usually between about 1 and 3 inches. 9

The invention is of particular value in the manufacture of artificial filamentary material by extruding acetone solutionsof cellulose acetate into aqueous solutions of diethyleneglycol diacetate or of acetone, for instance as described in U.S. applications Serial Nos. 217,816, 323,788, 451,191 and 451,193, the latter filed by B. P. Hill and J. Downing August 20, 1954. It may however also be used with advantage in other wet-spinning processes, for example in the wet-spinning of acetic acid .solutions of cellulose acetate, using as coagulant aqueous acetic acid which may contain in solution a high concentration of a salt, e.g. an alkali metal acetate. The acetic acid solutions of cellulose acetate may be primary or secondary acetylation solutions in which the catalyst has been neutralised, and if necessary the concentration of cellulose acetate adjusted, as by the addition of further acetic acid, to give the solution a suitable spinning viscosity.

Apparatus in accordance with the invention is illustrated in the accompanying drawing, which shows diagrammatically and in section a form of wet-spinning apparatus embodying the invention.

Referring to the drawing, the wet-spinning apparatus illustrated comprises a cylindrical extrusion chamber 1.

of relatively large diameter, e.g. about 8 inches, containing an upwardly facing spinning jet 2 fed by a pipe 3. A feed pipe 4 for coagulating liquid leads to the base of the extrusion chamber 1 via branches 5, two of which are shown. A metal gauze 6 extends across the extrusion chamber 1 below the level of the jet, and serves to even out the flow of coagulating liquid and render it substantially non-turbulent.

A setting tube 7 extends upwardly from the extrusion chamber 1, into which it opens directly opposite and between 0.25 and 4 inches from the face of the jet 2. The lower (input) end of the setting tube is flared so as to promote streamline and non-turbulent flow of the coagulating liquid into the tube. The setting tube may be of uniform diameter throughout its length, or its diameter may decrease in one or more stages as described in US. application S. No. 451,191. At its upper end the setting tube carries a collector head 8 provided with a liquid run-off 9. a v

Vertically above the open upper end of the setting tube 7 is a stripping device comprising an inverted funnel 10 and, above its stem '11-, a 'pigtail yarn-guide 12. The diameter and angle 'ofthe'funn'el are such that liquid running down its sides falls into the collector head 8 clear of the open upper end of the setting tube'7.

Above the stripping device is a godet '13, which preferably has a fluted surface as described in US. application '5. No. 451,193, filed September 2,1953, andbeyond this a washing device 14 and a second godet 15. The washing device 14 comprises a bath 16 for a washing liquid, provided with an inlet 17 for fresh washing liquid and-an outlet 18 for contaminated liquid; apair of driven thread-advancing rollers 19 having their axes skew with respect to each other are mounted in the bath partly above and partly below the operating level of the liquid surface. 7

In operation a coagulating liquid, for example aqueous ethylene glycol diacetate, is caused to flow through the pipe 4 and its branches into the extrusion chamber 1, past the jet 2, and up through the settingtube 7, from the top of which it overflows into the collector .head 8 which it leaves by the run-off 9. At thesame time a spinning solution, for example an acetone solution of cellulose acetate, is fed to the jet 2 by the feed pipe 3 and extruded in the form of filaments 20'intothe coagulating liquid in the extrusion chamber 1. The filaments formed travel with, but faster than, the coagulating liquid up the setting tube 7, from which they are drawn under tension by means of the godet 13. After leaving the setting tube 7 the filaments, now in the form -of-afbundle or yarn 21, pass through the inverted'funnel 'and the pigtail yarn guide 12. ,Coagulating liquid wiped 01f by means of the yarn guide 12 or the stem '11 of the inverted funnel flows down the wall of the f unnel and falls into the collector head 8. From the godet the yarn 21 passes to the washing device 14 in which ituiswashed for example with water; it is then forwarded by the 'second godet to a further treating device or a'zcoll'ecting device of any desired and suitable type.

As-an example of suitable dimensions for the inverted funnel 10, it may be said that if the-stripping device described, consisting of the funnel and the'yarncguide, is employed in the. processes of Examples 1-3 of U. S. application S. No. 323,788, in which yarns of cleniers ranging from about 60 to 1500 are made, the diameter of the funnel may be 2 inches at its base and 0.15 inch -at its apex, and the apex may be about 2 inches above the upper end of the setting tube 7.

Having described our invention what we desire to secure by Letters Patent is:

l. A wet spinning apparatus comprising a fixed extrusion chamber, an upwardly facing spinning jet in the spinning chamber, a setting tube of smaller diameter than the spinning chamber rigidly fixed to, opening into and rising vertically from it coaxially with the spinning jet and open at its upper end, means for causing a liquid to -flow through the extrusion chamber and the setting tube, and means for drawing filamentary material through and out of the setting tube under tension, to stretch it in the setting tube, and which also comprises in combination, vertically above and spaced from the upper end of the tube, stationary means for wiping adherent liquid from filamentary "material which has passed through the setting tube and means for directing the liquid so wiped ofl clear of the upper end of the setting tube, said directing means comprising an inverted funnel wholly above and coaxial with the setting tube and having asdiam- -eter at its base greater than that of the upper end of the setting tube.

2. Apparatus according to claim 1, wherein the diameter of the base of the funnel is 3-10 times that of the upper end of the setting tube.

3. Apparatus according to claim 1, wherein the apex of the funnel is l-3 inches above the upper end of the setting tube.

4. Apparatus according to claim 2, wherein the apex of the funnel is 1 to 3 inches above the upper end of thesetting tube.

5. Apparatus according to claim 3, comprising vertically above the funnel a pig-tail yarn guide adapted to make contact with filamentary material which has passed through the funnel and to wipe adherent liquid off the said material while maintaining its direction of travel unchanged. 1

References Cited in the file of this patent UNITED 'STATES PATENTS 827,434 Friedrick July 31, 1906 2,027,419 Dreyfus Jan. 14, 1936 2,054,852 Dreyfus Sept. 22, 1936 2,156,923 Picard May .2, 1939 2,453,839 Furness Nov. .16, 1948 2,536,093 Coleman et al. 'Jan. 2, 1951 2,552,598 Sowter et al "May 15, 1951 2,642,333 Tomonari June 16, 1953 2,758,909 Taylor et al. Aug. 14, 1956 2,788,256 Allen -Apr. 9, 1957 FOREIGN PATENTS 484,605 Great Britain May 9, 1938 

